They could create another Hawk area in Stormcloak territory to address the RP issue (there are actually over a dozen in Winterhold Hold but they aren't concentrated like they are in Solitude). Regarding the harvesting numbers, you're assuming a 1 feather to 1 arrow ratio for crafting which doesn't have to be the case. As I posted earlier while it's not particularly realistic to have 1 feather cover 20 arrows, it's also not particularly realistic to have a hawk yield only 1-3 feathers. It's a balance issue regarding the power of feathers to cure disease (and not a particularly serious one either - I usually collect over 2 dozen cure disease potions and hawk feathers during the course of doing the Companions quest due to the ignorant belief of Silver Hands that lycanthropy is a communicable disease, and there's an abundance of Shrines in the game) and it would be a balance issue of making harvesting them practical to have 1 feather cover several arrows.
Ok, that would work, but I personally would hate having to do it. I spend far too much time scouring the [ground] horizon for bears and cats as my archer; I very rarely look skyward (unless the dragon music starts of course), and have never yet felt the inclination to go shooting hawks. Also the Comp Quest is VERY optional (I personally did it once, didn't enjoy it and won't do it again)......
Hmm.., actually on second thoughts no. If you're going to implement a new crafting method, then you'd have to compare with what already exists. You'd have to compare feathers to leather, as being the plentiful non-lvl dependent ingredient. Therefore they'd have to give all blacksmiths a stock of feathers. Which again would make catching diseases a non issue.
Ok 3rd option (which might just work). Introduce a new item just called `feathers`, that is not an ingredient and is soley used for crafting. Have Hawks and maybe Hargravens drop them (in addition to what already exists), and have Blacksmiths and shops sell them ( logically fletchers would have the most). Cost should obviously be balanced. Maybe have bandits (bandit archers in particular) drop them too.
That way, it doesn't upset any existing balances, doesn't make Bosmer `resist disease` pointless even at low lvls, doesn't need any new spawn areas and maybe works. I just don't see the majority of people being too happy, with the thought of having to go and shoot hawks in very particular areas every time they wanted to make new arrows.
IRL (so I've just read) most arrow feathers were goose in the old world and turkey in the new world, but since neither exist in Skyrim, I'm not sure what they make all the arrows with...maybe chicken feathers?
Apologies for the long, rambling tone, been a long,rambling type of day....